Process for the manufacture of three-dimensionally crimped fibers and filaments

ABSTRACT

A process is described for making three-dimensionally crimped fibers and filaments from synthetic high-polymers. Fibers and filaments with a double refraction gradient over their crosssectional area, which have been obtained by known methods, are drawn and subsequently dried at temperatures within the range of from 50* to 230*C without any shrinkage. After drying, the crimp is developed at temperatures within the range of from 60* to 230*C with the filaments being free from any tension.

United States Patent 191 Biittner et al.

[54] PROCESS FOR THE MANUFACTURE OF THREE-DIMENSIONALLY CRIMPED FIBERSAND FILAMENTS Inventors: Gert Biittner; Ingoli Jacob, both of Bobingen,Germany Farbwerke Hoechst Aktiengesellschait vormals Meister Lucius &.Bruning, Frankfurt am Main, Germany Filed: May 27, 1970 App]. No.:41,051

Assignee:

[30] Foreign Application Priority Data June 3, 1970 Germany ..P 19 28243.0

U.S. Cl ..28/72.l7, 264/168 Int. Cl. ..D02j l/22 Field of Search..28/72.1, 72.17, 72; 264/168,

[56] References Cited UNITED STATES PATENTS 3,188,714 6/1965 Spangler..28/72.17

[ Jan. 16, 1973 Maerov et al ..28/72.17 X Kilian ..264/l68 Higginbotham...264/237 Reese ..28/72.17 X Jacob et al. 264/237 Primary ExamineP-LouisK. Rimrodt Attorney-Connolly and Hutz ABSTRACT free from any tension.

10 Claims, No Drawings PROCESS FOR THE MANUFACTURE OF THREE-DIMENSIONALLY CRIMPED FIBERS AND FILAMENTS The present invention relatesto a process for the manufacture of three-dimensionally crimped fibersand filaments.

Various processes have been proposed for making polyester filamentshaving a helical crimp which is very similar to the natural crimp ofwool. The common principle of these processes consists in subjecting thefilaments which have been freshly spun in the melt and are still hot toa rapid unilateral cooling carried out immediately below the spinningnozzle. The cooling may be brought about by unilaterally blowing the hotfilaments with cold air as described in U.S. Pat. No. 3,050,821, or bymeans of a thin liquid film on a porous hollow body as in British Pat.No. 809,273, or in a dry way on an appropriate cooling body as disclosedin Belgian Pat. No. 708,919. In all these processes, the unilateralcooling of the spun filaments in the plastic state results in anorientation of the macromolecules which decreases over thecross-sectional area of the filament from the cooled to the warm side ofthe filament. This orientation gradient is preserved during thefollowing drawing process and produces a latent crimp because the twosides of the filament have different capabilities of contracting. Thecrimp can then be developed by heating the drawn dried filaments whileallowing them to shrink.

Various processes have been described for developing a latent crimp.According to one of these proposals, the drawn filaments are heated;before heating, the filaments are advantageously cut to staple length.The fiber is heated without tension for minutes at 140C in hot air (cf.U.S. Pat. No. 3,050,821).

In another known process, the crimp is developed in such tows afterdrawing either by passing the two through a heating zone disposedbetween two conveying devices or by suspending loose ropes of the two ina heated oven forfree shrinking (cf. British Pat. No. 809,273).

These known processes suffer from the disadvantage that, prior todeveloping the crimp, the fibers and filaments must be dried completelyat low temperatures, for example filaments of polyethylene terephthalateat a temperature below 60C, in order to preserve the orientationgradient over the cross-sectional area during drying. When drying iscarried out at elevated temperatures, the differences in orientation arelevelled in the individual filaments so that the original latent crimpcannot be developed because it has been destroyed by drying.

The present invention provides a process for the manufacture ofthree-dimensionally crimped fibers and filaments of synthetichigh-polymers, preferably polyesters, and more particularly polyethyleneterephthalate, starting from filaments or tows to which a latent crimphas been conferred by producing an orientation gradient over thecross-sectional area, which process comprises drawing the filaments ortows, drying them at temperatures within the range of from 50C to 230Cwithout permitting shrinkage, and finally developing the crimp attemperatures within the range of from 60C to 230C in the absence of anytension.

In a preferred mode of executing the process of the invention, the drawnfilaments or tows are dried at a temperature within the range of from50C to 230C without permitting shrinkage, then cooled to a temperaturebelow 50C also without permitting shrinkage, and finally subjected to aheat treatment at a temperature within the range of from C to 230C,preferably C to C, without any tension in order to develop the crimp. Inanother advantageous form of the process of the invention, the drying iscarried out in a temperature range the lower limit of which is 20C belowthe second order transition temperature and the upper limit of which isat least 35C below the melting point of the filaments, and preferablyat. a temperature within the range of from 90C to C.

The process in accordance with the invention is preferably carried outsuch that the filaments or the two are or is after-drawn during dryingand cooling by 1 to 50 percent, preferably 1 to 10 percent, calculatedon the length of the filaments or the tow before said after drawing. Allprocess steps are advantageously carried out in a continuous manner on amoving tow.

The process of the invention can be carried out in in dustry in a simplemanner with the usual devices. The undrawn filaments, either a small.number thereof or a thick tow (for example 500,000 dtex), are passedthrough a brightening bath containing the substances commonly used forfavorably influencing the sliding and adhesion properties of the fibersand preventing electrostatic charge. The filaments or the tow are thensqueezed-off and drawn between two septet rollers. The drawn tow isconducted over a further two drawing devices which act in he same way asthe two first conveying devices used for the main drawing process. Thethird roller unit has at least the same conveying speed as the secondroller unit, while the fourth roller unit has at least the sameconveying speed as the third roller unit so that the tow cannot shrinkbetween the second and the third drawing device during drying. It isadvantageous to after-draw the tow during drying as well as duringcooling by 1 to 50 percent, preferably 1 to 10 percent.

The distances between the individual drawing devices depend on thepossibilities of drying and cooling and are such that the tow, whenleaving the fourth drawing device, has been dried completely and cooledto below 50C. Drying is performed on the second drawing device if asufficient amount of heat can be supplied to the rollers thereof bymeans of steam or heating liquid. Alternatively the tow may be driedbetween the second and the third. drawing device on a heated metalsurface, in hot air, by infrared heating or in a high-frequencyelectromagnetic alternating field. Drying is advantageously carried outin a temperature range the lower limit of which is 20C below the secondcapable of eliminating a sufficient amount of heat from the tow.

Under certain conditions, the process may also be carried out using onlythree drawing devices. In this case, the brightening agent is applied tothe undrawn tow before drawing and thoroughly squeezed-off. The tow isthen drawn between the first and the second roller unit. The secondroller unit is kept at a sufficiently high temperature by a heatingliquid or superheated steam so that the tow is completely dry whenleaving this roller unit. The third drawing device may be cooled by acirculating liquid to such an extent that the tow has been cooled tobelow 50C when it leaves the rollers.

It is advantageous to sufficiently precool the tow in this case betweenthe second and the third drawing device on a cooled metal surface orsimply in air.

If the crimp is only developed after cooling, it is an essential featureof the process of the invention to cool the tow which has been driedcompletely to a temperature below 50C before reducing the tension, thatis before allowing the tow to shrink.

After having been released from tension, the completely dry andsufficiently cooled tow has a slight crimp in large bends and theindividual filaments do not stick together. To develop the crimp the towis now subjected to a heat treatment at a temperature within the rangeof from 60C to 230C, preferably 90C to 130C, in a gaseous or liquidheating medium. The tow should be as free from stress as possible sincethe quality of the crimp which is being developed is considerablydeteriorated even by the slightest tension in the direction of the axisof the filament, for example by the weight of 1 meter of filament. Byquality of the crimp there is here meant the number of bends percentimeter of length of filament, the crimp retentivity and the recoveryof the temporarily stuffed fibers. It has been found, for example, thatwhen the crimp is developed between two neighboring conveying units thedevelopment of an optimum crimp is prevented by the tensile stressproduced by the dead weight of the tow, even when the second conveyingunit revolves so slowly that the tow sags a little. This tensile stressmakes itself felt to the same extent in each place of the tow betweenthe two conveying units. Contrary thereto, a considerably smaller stressis obtained in a simple manner if the tow is freely suspended andsubjected only to the action of gravity. At the lower end of the tow thestress is equal to zero. In a continuously moving tow, the stress isvery near this limiting value when the tow is run off, for example, in aperpendicular direction from a conveying unit onto a horizontallyarranged conveyor belt disposed below, which conveys the tow.Immediately before striking the conveyor belt, the tow is under aminimum tensile stress. When it is blown at this point with steam or hotair, a fiber is obtained the crimp of which is superior as regards itsquality to that of all other fibers obtained by a continuous process.

The crimped tow is fed by the horizontal conveyor belt to devices usedfor the continuous processing of the tow. The crimp is generallysubjected to a thermosetting with the help of steam or hot air. Thethermosetting as well as the cutting and packaging of the finishedfibers may be carried out continuously in known manner.

The above fully continuous process enables the production of a fiberwhich has a crimp that is similar to that of native fibers and adimensional stability that excels that of the known synthetic fibers.

The process in accordance with the invention is particularly suitablefor the production of crimped filaments, fibers or tows of linearpolyesters of high molecular weight. It is advantageously applied tolinear polyesters of high molecular weight of which the acid componentconsists of at least mol percent terephthalic acid units and the diolcomponent consists of at least 90 mol percent ethylene glycol units.

The process is also applicable to fibers, filaments and tows ofcopolyesters or polyester amides.

After the valuable properties of helically crimped fibers and filamentshave become known, an economic process for their manufacture is ofinterest to industry. In the fibers crimped in known manner in stuffingchambers, the crimp is limited to the places of bending. In said placesof bending, the fiber has been strongly changed morphologically, whichunfavorably affects the crimp retentivity. Contrary thereto, the helicalcrimp obtained in accordance with the invention is uniformly distributedover the entire length of the fiber as is the case with native fibers,so that the dimensional stability of fleeces or textile shapedstructures made of such fibers is considerably improved.

Owing to these valuable properties, the fibers obtained by the processof the invention find new fields of application. They are suitable foruse in all cases in which fibers having a good bulkiness combined with agood recovery from load are required.

The following Examples serve to illustrate the invention.

EXAMPLEI A tow of 10 000 monofilaments which, during melt spinning, hadbeen cooled on one side on a metal surface directly below the spinningnozzle and therefore had an orientation gradient, was passed at a rateof 23 m/min. through a brightening bath comprising an aque ous solutionof an allyl phenyl polyglycol ether, aliphatic polyglycol ethers andfatty acid esters of dihydric alcohols, squeezed off and drawn in knownmanner in steam in the ratio of l 2 between two 7- roller drawingdevices. The spun filaments had been obtained by the process describedin Belgian Pat. No. 708 919. The drawn tow was passed over a further twodrawing devices, the third drawing device revolving 1.04 times fasterthan the second drawing device, and the fourth drawing device revolving1.04 times faster than the third drawing device. Between the second andthe third septet a metal body 4 meters long and 50 centimeters wide, ofwhich the surface was heated at 140C was disposed. Through the rollersof the third and fourth septet cooling water was passed in order to coolthe tow on the roller surface to about 30C. From the last roller of thefourth septet, the tow was allowed to fall freely 1 meter verticallydownward onto a conveyor belt. Directly above the latter, superheatedsteam at a temperature of about C was blown from both sides through thetow to develop the crimp, whereby the speed of the tow was stronglyreduced. With a speed of rotation of 50 m/min. of the rollers of thefourth septet, the speed of the conveyor belt was adjusted to 10 m/min.The tow was conveyed by the conveyor belt to a heated channel in whichit was heated to a temperature of 150C within 60 seconds by hot air.After having left the setting channel the tow was allowed to cool andthen cut in known manner.

The fiber so obtained had the following properties:

Tensile strength 3.1 p/dtex Elongation at break 25 percent K 1 20.3percent K 15.3 percent Crimp retentivity 75.5 percent Crimp 4 to 5bends/cm 1 1 o)/ 1' 100 I distance between grips (length of crimpedfiber under a preliminary tension of 1.8 mp/dtex) l length of the fiberafter it has been de-crimped without any further drawing 2= 2* .0/ 2 100I length of the fiber after it has been de-crimped without any furtherdrawing and then loaded and released; K is measured after loading thefiber with 0.5 p/dtex for 1 minute and allowing it to recover for 1minute.

EXAMPLE2 In the manner described in Example 1, a tow of 50,000monofilaments obtained by the process of the above Belgian Patent andhaving an orientation gradient was passed at a rate of 23 m/min. througha brightening bath, squeezed-off and then drawn in steam between twoseptets. The rollers of the second septet were heated with superheatedsteam to a surface temperature of 100C so that the tow was completelydried after drawing. The distance between the second and the thirdseptet was meters. Here the tow cooled substantially in air at roomtemperature. The rollers of the third septet rotated at a speed of 48m/min., that is 1.04 times faster than the second septet. They werecooled with water so that the tow had been completely cooled when itleft the third septet. The tow was subjected without tension to a heattreatment to develop and set the crimp in the manner described inExample 1. The properties of the fiber corresponded to those indicatedin Example 1.

What is claimed is:

1. A process for the manufacture of three-dimensionally crimpedfilaments or tows of synthetic highpolymers, starting from filaments ortows to which a latent crimp has been conferred by producing anorientation gradient over the cross-sectional area, which processcomprises drawing the filaments or tows, drying them at a temperaturewithin the range of from 50C to 230C without permitting shrinkage, andfinally developing the crimp at a temperature within the range of from60C to 230C in the absence of any tension.

2. The process of claim 1 wherein the drawn filaments or the tow are oris dried at a temperature within the range of from 50C to 230C withoutpermitting shrinkage, cooled to a temperature below 50C withoutpermitting shrinkage, and subjected without any tension to a heattreatment within the range of from 60C to 230C to develop the crimp.

3. The process of claim 1 wherein the crimp is developed at atemperature within the range of from 90C to 130C.

4. The process of claim 1 wherein drying is carried out in a temperaturerange the lower limit of which is 20C below the second order transitiontemperature and the upper limit of which is at least C below the meltingpoint of the filaments.

5. The process of claim 1 wherein drying is carried out at a temperaturewithin the range of from 90C to 160C.

6. The process of claim 1 wherein the filaments or the tow is or areafter-drawn during drying and cooling by l to 50 percent calculated onthe length of the filaments or the tow before said after-drawing.

2. The process of claim 1 wherein the drawn filaments or the tow are oris dried at a temperature within the range of from 50*C to 230*C withoutpermitting shrinkage, cooled to a temperature below 50*C withoutpermitting shrinkage, and subjected without any tension to a heattreatment within the range of from 60*C to 230*C to develop the crimp.3. The process of claim 1 wherein the crimp is developed at atemperature within the range of from 90*C to 130*C.
 4. The process ofclaim 1 wherein drying is carried out in a temperature range the lowerlimit of which is 20*C below the second order transition temperature andthe upper limit of which is at least 35*C below the melting point of thefilaments.
 5. The process of claim 1 wherein drying is carried out at atemperature within the range of from 90*C to 160*C.
 6. The process ofclaim 1 wherein the filaments or the tow is or are after-drawn duringdrying and cooling by 1 to 50 percent calculated on the length of thefilaments or the tow before said after-drawing.
 7. The process of claim1 wherein the filaments or the tow is or are after-drawn during dryingand cooling by 1 to 10 percent calculated on the length of the filamentsor the tow before said after-drawing.
 8. The process of claim 1 whereinall process steps are carried out continuously on a moving tow.
 9. Theprocess of claim 1 wherein the synthetic polymer is a polyester.
 10. Theprocess of claim 1 wherein the synthetic polymer is polyethyleneterephthalate.